scholarly journals Influence of Seasonal Variations of Temperature and Light on the Growth Rate of Cultures and Natural Populations of Intertidal Diatoms

1980 ◽  
Vol 2 ◽  
pp. 35-43 ◽  
Author(s):  
W Admiraal ◽  
H Peletier
Keyword(s):  
Growth Rate ◽  
Seasonal Variations ◽  
Natural Populations

scholarly journals Beyond demographic buffering: Context dependence in demographic strategies across animals

2021 ◽  
Author(s):  
Omar Lenzi ◽  
Arpat Ozgul ◽  
Roberto Salguero-Gomez ◽  
Maria Paniw
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Temporal Variation ◽  
Population Growth Rate ◽  
Natural Populations ◽  
Environmental Context ◽  
Context Dependence ◽  
Vital Rate ◽  
Rate Variation ◽  
Vital Rates

Temporal variation in vital rates (e.g., survival, reproduction) can decrease the long-term mean performance of a population. Species are therefore expected to evolve demographic strategies that counteract the negative effects of vital rate variation on the population growth rate. One key strategy, demographic buffering, is reflected in a low temporal variation in vital rates critical to population dynamics. However, comparative studies in plants have found little evidence for demographic buffering, and little is known about the prevalence of buffering in animal populations. Here, we used vital rate estimates from 31 natural populations of 29 animal species to assess the prevalence of demographic buffering. We modeled the degree of demographic buffering using a standard measure of correlation between the standard deviation of vital rates and the sensitivity of the population growth rate to changes in such vital rates across populations. We also accounted for the effects of life-history traits, i.e., age at first reproduction and spread of reproduction across the life cycle, on these correlation measures. We found no strong or consistent evidence of demographic buffering across the study populations. Instead, key vital rates could vary substantially depending on the specific environmental context populations experience. We suggest that it is time to look beyond concepts of demographic buffering when studying natural populations towards a stronger focus on the environmental context-dependence of vital-rate variation.

scholarly journals Estimating abundance of the Endangered onager Equus hemionus onager in Qatruiyeh National Park, Iran

Oryx ◽  
2013 ◽  
Vol 47 (2) ◽  
pp. 266-272 ◽  
Author(s):  
Mahmoud-Reza Hemami ◽  
Moslem Momeni
Keyword(s):  
Growth Rate ◽  
Protected Area ◽  
National Park ◽  
Natural Populations ◽  
Distance Sampling ◽  
Line Transect ◽  
Management Interventions ◽  
Equus Hemionus ◽  
Wild Ass ◽  
Semi Arid

AbstractHistorically, the onager or Persian wild ass Equus hemionus onager, endemic to Iran, was widespread on the arid and semi-arid central steppes but only two natural populations remain. We estimated the population density of the onager in Qatruiyeh National Park using line transect distance sampling. Transects were surveyed on three plains in the Park and the results compared with total counts conducted by the Department of Environment. Our estimate (109 onagers per 100 km2; 95% confidence interval 67–179) is similar to that obtained by the total counts (137 onagers per 100 km2). Distance sampling is therefore a promising method for estimating the abundance of the onager. Using the annual censuses performed by the Department of Environment over the last 13 years we estimated that the population has a growth rate of 0.09. During the same period the onager population in the Touran Protected Complex has experienced a severe decline. The high density of onagers within the National Park indicates the unsuitability of adjacent habitats, including Bahram-e-Goor Protected Area, for this species. Lack of sufficient security and poorly distributed water sources appear to be the main reasons discouraging onagers from entering the Bahram-e-Goor Protected Area. We recommend and describe management interventions that could potentially assist in maintaining the last surviving onager populations in Iran.

Population dynamics of an Egyptian desert shrub, Thymelaea hirsuta

1997 ◽  
Vol 75 (12) ◽  
pp. 2027-2037 ◽  
Author(s):  
Ali El-Keblawy ◽  
K. H. Shaltout ◽  
J. Lovett-Doust ◽  
A. Ramadan
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Seedling Recruitment ◽  
Natural Populations ◽  
Plant Size ◽  
Population Variation ◽  
Adult Survival ◽  
Thymelaea Hirsuta ◽  
Egyptian Desert

Natural populations of the evergreen shrub, Thymelaea hirsuta (L.) Endl., were studied over 6 years at five desert habitats, in terms of seedling recruitment and adult survival and as a function of plant size and gender class. Habitat and time significantly influenced mortality of both reproductive and non-reproductive plants. Plant size also significantly affected adult mortality. Seedling recruitment varied significantly with habitat and year and approached zero some years. Significant among-year and among-population variation in population growth rates were observed over the 6 years of study, and all populations declined in size (ranging from −1.7% per year at the coastal dune site to −10.9% per year at the inland plateau site). Spearman rank correlation analysis between habitats ranked according to a north–south gradient and demographic variables indicates that this gradient is associated with a pattern of lower seedling emergence and survival and a lower population growth rate and greater mortality for all size-classes of Thymelaea plants. In experimental botanic garden plots, germination of seed collected from five natural populations, and seedling survival in the following year were assessed under conditions of high, medium, and low seedling density. Seedling emergency differed significantly according to maternal habitat. With regular watering, seeding survival to one year was 72% (averaged across habitats and densities). This compares with 64% for seedlings grown at the highest density, suggesting that the intense mortality observed under field conditions is more likely to be a result of water shortage than intraspecific competition. Key words: Egyptian desert, Thymelaea hirsuta, germination and establishment, seedlings, recruitment, competition, population growth rate.

Silage and hay intakes of housed red deer calves

1990 ◽  
Vol 1990 ◽  
pp. 77-77
Author(s):  
D J Kennedy
Keyword(s):  
Growth Rate ◽  
Seasonal Variations ◽  
Red Deer ◽  
Slow Growth ◽  
Red Meat ◽  
Limiting Factor ◽  
Low Fat ◽  
Slow Growth Rate ◽  
Quality Diet ◽  
Ad Libitum

There is an increasing interest in deer farming as an alternative livestock enterprise. One of the main reasons for this is that, currently, demand for venison (a low fat, red meat) is much greater than supply. However a major limiting factor to venison production is the slow growth rate of deer during the winter months. This is a consequence of their low feed intakes over this period. The aim of this study was to monitor feed intakes of housed, commercially-farmed red deer calves on a ‘good quality’ diet over the winter months to observe seasonal variations in appetite.One hundred and fifty four red deer calves (mainly June born) were observed in this study. There were four pens of stags containing 25, 23, 22 and 13 animals per pen, and three pens of hinds with 25, 25 and 21 animals per pen. All animals were offered forage ad-libitum plus 1.36 kg/d of a home-mix ration (12.9 MJ ME/kg DM, I62g CP/kg DM). One group of hinds was offered hay as the forage whilst the others all received silage.

A NONAUTONOMOUS MODEL FOR THE INTERACTIVE EFFECTS OF FEAR, REFUGE AND ADDITIONAL FOOD IN A PREY–PREDATOR SYSTEM

2021 ◽  
pp. 1-39
Author(s):  
NAZMUL SK ◽  
PANKAJ KUMAR TIWARI ◽  
YUN KANG ◽  
SAMARES PAL
Keyword(s):  
Growth Rate ◽  
Hopf Bifurcation ◽  
Seasonal Variations ◽  
Positive Periodic Solution ◽  
Oscillatory System ◽  
Interactive Effects ◽  
Predator Population ◽  
Prey Refuge ◽  
Additional Food ◽  
Predator System

The importance of fear, refuge and additional food is being increasingly recognized in recent studies, but their combined effects need to be explored. In this paper, we investigate the joint effects of these three ecologically important factors in a prey–predator system with Crowly–Martin type functional response. We find that the fear of predator significantly affects the densities of prey and predator populations whereas the presence of prey refuge and additional food for predator are recognized to have potential impacts to sustain prey and predator in the habitat, respectively. The fear of predator induces limit cycle oscillations while an oscillatory system becomes stable on increasing the refuge. The system first undergoes a supercritical Hopf-bifurcation and then a subcritical Hopf-bifurcation on increasing either the growth rate of prey or growth rate of predator due to additional food. Increasing the quality/quantity of additional food after a certain value causes extinction of prey species and rapid incline in the predator population. An extension is made in the model by considering the seasonal variations in the cost of fear of predator, prey refuge and growth rate of predator due to additional food. The nonautonomous model is shown to exhibit globally attractive positive periodic solution. Moreover, complex dynamics such as higher periodic solutions and bursting patterns are observed due to seasonal variations in the rate parameters.

Extracellular production in relation to growth of four planktonic algae and of phytoplankton populations from Lake Ontario

1969 ◽  
Vol 47 (3) ◽  
pp. 405-413 ◽  
Author(s):  
C. Nalewajko ◽  
L. Marin
Keyword(s):  
Growth Rate ◽  
Environmental Factors ◽  
Carbon Fixation ◽  
Natural Populations ◽  
Lake Ontario ◽  
Dry Weight ◽  
Weight Basis ◽  
Extracellular Production ◽  
Relative Growth ◽  
Planktonic Algae

In four species of planktonic algae both carbon fixation and excretion on an ash-free dry weight basis increase with relative growth rate (K) of the culture measured in log10 units. In natural populations percentage excretion values are positively correlated with K values; however, environmental factors may be of relatively greater importance and determine the extent of excretion.

scholarly journals Seasonal variations in active dispersal of natural populations of Triatoma infestans in rural north-western Argentina

2006 ◽  
Vol 20 (3) ◽  
pp. 273-279 ◽  
Author(s):  
G. M. VAZQUEZ-PROKOPEC ◽  
L. A. CEBALLOS ◽  
P. L. MARCET ◽  
M. C. CECERE ◽  
M. V. CARDINAL ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Natural Populations ◽  
Triatoma Infestans ◽  
Active Dispersal ◽  
North Western

The physical and biochemical condition of Modiolus modiolus (L.) in selected Shetland voes

1981 ◽  
Vol 80 ◽  
pp. 299-321
Author(s):  
C. A. Comely
Keyword(s):  
Growth Rate ◽  
Density Distribution ◽  
Seasonal Variations ◽  
General Survey ◽  
Modiolus Modiolus ◽  
Environmental Variations ◽  
Biochemical Condition ◽  
Scottish Lochs

Synopsis1. A general survey of the sub-tidal populations of Modiolus modiolus (L.) to a depth of 18 or 21 m was carried out in five Shetland voes, with particular emphasis in Sullom Voe. Estimations of density distribution and growth rate were made.2. Commencing in June 1976 samples were collected at three-monthly intervals from two sites in Sullom Voe, and from one site in Cat Firth in 1977, to investigate seasonal variations in flesh and biochemical content. The data indicate that Shetland Modiolus are generally similar in their biology to those from Scottish lochs, and are liable to considerable variation between and within populations, with groups responding to environmental variations of very local extent.3. A list of animals found associated with Modiolus and their byssus complexes is given. As no effort was made to collect the fauna systematically or quantitatively, the list is not comprehensive.

The evolution of growth trajectories and other complex quantitative characters

Genome ◽  
1989 ◽  
Vol 31 (2) ◽  
pp. 778-783 ◽  
Author(s):  
Mark Kirkpatrick ◽  
David Lofsvold
Keyword(s):  
Growth Rate ◽  
Genetic Variation ◽  
Degrees Of Freedom ◽  
Natural Populations ◽  
Genetic Data ◽  
Growth Trajectories ◽  
Infinite Dimensional ◽  
Quantitative Characters ◽  
Method Analysis ◽  
Complex Characters

Growth trajectories differ from many other quantitative, characters in that they are characterized by a continuous function rather than by a finite number of discrete measurements. We review here recently developed methods for predicting the evolution of growth trajectories under the influence of natural or artificial selection. Using our method, analysis of genetic data from mice shows that the patterns of genetic variation arising from developmental processes impose constraints on evolution of growth trajectories. These constraints can be quantified to reveal the families of growth trajectories that can be produced by selection and those families that cannot. The data suggest there may be relatively few evolutionary degrees of freedom for growth trajectories despite the presence of abundant additive genetic variation to alter size and (or) growth rate at every age. The description of these constraints may be useful to both biologists who would like to determine the evolutionary options available to natural populations and to breeders who would like to alter growth trajectories to economically improve domesticated species. Our methods and conclusions can be generalized to other kinds of "infinite-dimensional" or complex characters, including morphological shapes and norms of reaction.Key words: growth trajectories, quantitative genetics, constraints, infinite-dimensional characters, body size.

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